20
Important Concepts
1. Electrophilic Reactivity – of the carbonyl carbon
in carboxylic acid derivatives:
• Weakened by good electron-donating substituents
•
Affect accounts for increased basicity:
•
•
Alkanoyl halides < anhydrides < esters < amides
With amides, the large effect causes hindered rotation
about the amide bond on the NMR time scale.
2. Nomenclature – of carboxylic acid derivatives:
•
•
•
•
•
Alkanoyl halides
Carboxylic anhydrides
Alkyl alkanoates
Alkanamides
Alkanenitriles
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Important Concepts
3. IR Spectroscopy – of carboxylic acid derivatives:
•
•
•
•
Alkanoyl chlorides – 1790-1850 cm-1
Anhydrides – 1740-1790 cm-1 and 1800-1850 cm-1
Esters – 1735-1750 cm-1
Amides – 1650-1690 cm-1
4. Reactions of Carboxylic Acid Derivatives
•
•
•
•
Water – (acid or base catalysis) hydrolyze to
corresponding carboxylic acid
Alcohols – react to form esters
Amines – react to form amides
Grignard Reagents – react to form ketones
•
•
Esters may react further to form alcohols.
Hydrides – react to form aldehydes, alcohols or
amines
20
Important Concepts
5. Natural Products
•
•
Waxes – long-chain esters
Oils and Fats – triesters of glycerol
•
•
Hydrolysis yields soaps
Phospholipids – triglycerides containing phosphoric
acid ester sub-units.
•
From micelles and lipid bilayers due to polar head and
hydrophobic tail
6. Transesterification – used to convert one ester
into another
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Important Concepts
7. Nitrides – similar to alkynes; carbon and nitrogen
are sp2 hybridized.
• IR - ~2250 cm-1 stretch
• NMR – adjacent protons are deshielded; 13C
absorption for nitrile carbon is at low field (δ ~ 112126 ppm)
8. Mass Spectrometry – Magnetic separation of
ionized molecules on the basis of molecular weight
• Ionizing beam may fragment molecules into smaller
particles which are separated and recorded as the
mass spectrum.
• Certain elements (Cl, Br) produce recognizable
isotopic patterns.
• The fragmentation patterns can be used to deduce
the structure of a molecule.
20
Important Concepts
9. High-Resolution Mass Spectrometry – allows
molecular formula determination from exact mass
values